306 ORIGIN OF LIFE IN AMERICA 



species of Hyalinia, a large number of Bulimuli, two Pupae, 

 one Leptinaria, a Succinea and a Helicina as having been 

 collected on the islands by previous visitors. He then dilates 

 upon the various accidental means of transport, and concludes 

 that the agency of winds and ocean currents is amply sufficient 

 to explain the origin of the molluscan fauna. He acknow- 

 ledges that the archipelago is situated within an almost wind- 

 less area, where storms are of rare occurrence, yet maintains 

 that during the course of ages the climatic features may have 

 been different from those obtaining at present. He also 

 emphasises the fact of the tenacity of life of mollusks and 

 the length of time they are able to subsist without food, claim- 

 ing that a theory which will fairly explain a good portion of 

 the phenomena of distribution by such agencies and operating 

 directly under our eyes, is preferable to those, however plau- 

 sible and attractive, involving conjectural and remoter con- 

 ditions. 



In his endeavour to support the theory of accidental dis- 

 tribution as applied to the origin of the Galapagos fauna, Dr. 

 Stearns seems to forget that no observation has ever been 

 made clearly indicating the conveyance of mollusks or their 

 eggs in drift-timber. Mollusks have never been found 

 in the crevices or under the bark either of trees encountered 

 on the sea or of those stranded on foreign coasts. Very 

 shortly after the trees are stranded, they are no doubt invaded 

 by all sorts of creatures seeking moisture and shelter ; but the 

 theory of accidental distribution, so ably advocated by many 

 eminent naturalists still involves a good deal of the conjecture 

 which Dr. Stearns is so anxious to avoid. Although Dr. 

 Ball * fully acknowledges that we possess no actual proof 

 in support of the drift-theory, he also concurs with Dr. 

 Stearns in the opinion that there can be little doubt of the 

 land snails having been introduced to the Galapagos islands 

 in that manner. In his review of the molluscan fauna of the 

 islands, he mentions thirty-three species of Bulimuli, two 

 species of Vitrea and one of Conulus, two Pupae, four 

 Succineae, one Tornatellina (Leptinaria), one Helicina and 

 finally one Endodonta. Of these forty-five species, only a 



* Dall, W. H., "Insular Land-shell Faunas." 



